Bioassay designs for validating biologically based mathematical models of carcinogenesis for risk assessment.

Bioassays that include various types of discontinuous exposure to carcinogens are somewhat rare and are far from routine. However, discontinuous-dosing groups represent a valuable enhancement of the ordinary bioassay design. My hope is that efforts to include discontinuous-exposure groups in cancer-bioassays will become widespread, and that discontinuous-dosing designs will eventually be a matter of routine. To me, such designs represent an easy (although perhaps costly) way to increase the sophistication of the tumor incidence data for model fitting, and to provide valuable data for validating (or perhaps invalidating) postulated mathematical models of the cancer process. Certainly discontinuous-dosing data at least provide a valuable ancillary resource to be utilized along with data on postulated mechanisms in the effort to implement biologically based models of the cancer process for quantitative risk assessment. Such data might even be indispensible.